Trump could win. If you don’t believe this, then you may not be able to put your distaste (or worse) aside and pull the lever for Hillary. If you don’t believe this, then you might conclude that it’s morally acceptable to stay at home on November 8. So I repeat, Trump could win. Here’s why.

Let’s start with Brexit. For most of the 10 months preceding the election, “remain” enjoyed a significant lead in the polls. The UK’s wagering markets reflected an even stronger conviction that Brexit couldn’t win, with Ireland’s largest bookie showing a 92% probability of a “remain” victory only a couple of days prior to the vote. Currency and financial markets agreed. But at the end of the day, 51.9% of those voting chose Brexit.

Why is the outcome on November 8 similarly difficult to predict? Both candidates have extraordinarily high unfavorable ratings. Recently the Real Clear Politics average of polls put the candidates within three percentage points (and some, such as the L.A. Times/USC tracking survey showed a statistical dead heat). This is a trailing indicator, with the momentum in Trump’s favor (Hillary’s lead has been cut in half during the last month). In early August the Time for Change forecasting model, which has correctly predicted the winner of the vote in every election since 1988, predicted a Trump win, 51.4% to 48.6% (putting a 66% probability on a Trump victory). Of course many take comfort in Trump’s poor showing in a number of key battleground states. But political experts agree that it is far too early to have confidence that Hillary’s margins in North Carolina, Florida, Nevada or Ohio will hold. Anything can happen.

And it already has. Trump has enjoyed a series of extraordinarily lucky, almost unbelievable, breaks. Who could have predicted that he would stand next to the Mexican President, treated like a visiting head of state, and that the Mexican leader would fail to call him out on his many calumnies against the Mexican people or state publicly that his country would not pay for The Wall? Inconceivable, but it happened. Who could have imagined that our once vigorous press, during last week’s foreign policy forum, would hit Mr. Trump the softest possible lobs, and fail to push back as he unleashed his usual combination of blather(my main qualification to be commander in chief “is, I have great judgment”), bizarreness (repeated praise of authoritarian President Putin’s alleged 82% approval rating and the assertion that our generals have been “reduced to rubble”) and dissemblance (saying he opposed the invasion of Iraq when he is on the record in 2002 as supporting it). If Trump receives this kind of free pass in the debates, the poll numbers could move significantly. Although Trump’s “ground game” and funding lag, this too could change quickly.

The ability of experts to predict the result is further undermined by the sui generis nature of this election. Instead of two campaigns managed by political pros who play by the same rules, we have one that has discarded the rule book and expressed open disdain for the orthodoxies of American politics. The politico class on both sides, which makes its living as the high priests of this orthodoxy, is generally predicting that things will not end well for Trump, and so they must. But the alarming fact is that no one really knows how to combat a campaign like Trump’s. His GOP primary opponents couldn’t figure it out, and all the organization and strategic advice that money could buy failed to stop him. Imagine a professional boxer stepping into the ring prepared to fight the fight he has fought dozens of times before, but instead, his opponent unleashes a flurry of moves he’s never seen, most of which violate the unwritten rules of the sport.

And then there is the world beyond the candidates’ control. Another terrorist attack in the United States could change the equation completely. A stock market slump or major stall in the economic recovery would add momentum to Trump. In an election where one the candidacies is propelled by an emotionally volatile mix of fear, anxiety, anger, and worse, external events could have a profound effect on voter sentiment. And now Hillary’s pneumonia, a powerful reminder that anything can happen.

So what’s my point? Complacency. It is the greatest friend of the demagogue and the greatest enemy of democracy. If Donald Trump wins this election, it will not be due to his core of ardent fans. The fault will lie with the millions of American voters who stay home on Election Day because of their ambivalence toward the other candidate and/or the mistaken belief that they are not needed to save the country from Mr. Trump.